What a half-hour or 45-minute time zone is#
A time zone's offset is how far its clocks run ahead of or behind UTC, the world time standard. Most zones use whole hours. A fractional offset adds minutes: UTC+5:30 is 5 hours 30 minutes ahead of UTC, and UTC+5:45 is 5 hours 45 minutes ahead.
Earth turns 15 degrees of longitude every hour, so one degree is 4 minutes of sun time. Britannica notes that ideal zones are 15-degree slices of the globe, but real borders and cities do not line up with them. A country whose sun time falls between two whole hours can choose the half or quarter hour in between.
Where the half-hour and 45-minute zones are#
A scan of the IANA time zone database (release 2025b, the release bundled with Node 22) for January 15, July 15 and October 9, 2026, lists 15 zone names with a fractional offset on at least one of those dates. They use 13 different offsets, and the main entries match timeanddate.com's list of half-hour and 45-minute zones. How Many Time Zones Are There? 24 on Paper, 39 in 2026 covers the whole world.
| Offset | Where | When |
|---|---|---|
| UTC-9:30 | Marquesas Islands (French Polynesia) | All year |
| UTC-3:30 | Newfoundland, Canada (NST) | Standard time |
| UTC-2:30 | Newfoundland | Summer time |
| UTC+3:30 | Iran | All year |
| UTC+4:30 | Afghanistan | All year |
| UTC+5:30 | India (IST) and Sri Lanka | All year |
| UTC+5:45 | Nepal (NPT) | All year |
| UTC+6:30 | Myanmar and the Cocos (Keeling) Islands | All year |
| UTC+8:45 | Eucla area, Western Australia | All year |
| UTC+9:30 | Northern Territory; South Australia and Broken Hill (New South Wales) | Territory all year; the others in standard time |
| UTC+10:30 | South Australia and Broken Hill; Lord Howe Island | Summer time; standard time |
| UTC+12:45 | Chatham Islands, New Zealand | Standard time |
| UTC+13:45 | Chatham Islands | Summer time |
As of October 9, 2026, the Chatham Islands have been on summer time since Sunday, September 27, and Adelaide, Broken Hill and Lord Howe Island (which shifts only 30 minutes, to UTC+11) since Sunday, October 4. Newfoundland is still on summer time and returns to UTC-3:30 on Sunday, November 1.
How India ended up on UTC+5:30#
Before 1906 there was no single Indian clock. Reference works say railways ran on Madras time, about 5 hours 21 minutes ahead of Greenwich, while Calcutta and Bombay kept their own times (How Time Zones Were Born: Railways, Telegraphs and the Day of Two Noons tells the wider story). The IANA database shows India's offset changing from UTC+5:21:10 to UTC+5:30 at the start of January 1, 1906.
New World Encyclopedia says the 82.5°E meridian, a line near Allahabad (now Prayagraj), was chosen in 1905 and took effect on January 1, 1906, also covering Ceylon (now Sri Lanka). Live History India gives the same start date, and Britannica says the zone matches Prayagraj, picked as the central meridian under British rule. The sum is 82.5 degrees / 15 degrees per hour = 5.5 hours.
Accounts say Calcutta and Bombay kept their own local times for some years after 1906, and that IST became the official time for the whole country after independence; sources differ on the dates.
The clock does not match the sun everywhere. India spans about 29 degrees of longitude (roughly 68°E to 97°E, in the figures the National Physical Laboratory used). At 4 minutes per degree that is about 2 hours of sun time, so solar noon comes almost two hours earlier in the far northeast than in the far west.
In 2018 the National Physical Laboratory, India's official timekeeper, argued that two zones are technically feasible: IST-I at UTC+5:30 and IST-II at UTC+6:30 for the northeast and the Andaman and Nicobar Islands. Searches found no sign that India has adopted it, so IST remains the only official time as of October 2026.
Why other places picked a half hour or 45 minutes#
Britannica gives the main reasons. Newfoundland's offset is close to local solar time in St. John's, where most Newfoundlanders lived, and Iran and Afghanistan were similar cases. Nepal's offset also sits close to the sun time at its capital. The table compares each city's sun time, which the IANA database records from before standard time, with today's clock.
| City | Sun time (IANA) | Clock today | The clock is off by |
|---|---|---|---|
| St. John's | UTC-3:30:52 | UTC-3:30 | 52 seconds |
| Tehran | UTC+3:25:44 | UTC+3:30 | 4 min 16 s |
| Kabul | UTC+4:36:48 | UTC+4:30 | 6 min 48 s |
| Kathmandu | UTC+5:41:16 | UTC+5:45 | 3 min 44 s |
| Yangon | UTC+6:24:47 | UTC+6:30 | 5 min 13 s |
| Calcutta | UTC+5:53:28 | UTC+5:30 | 23 min 28 s |
Calcutta is the odd one out because IST is a countrywide compromise, not one city's sun.
Clocks can also be set on purpose. Nepal used India's UTC+5:30 until the end of 1985, and the IANA data shows it moving 15 minutes ahead at the start of 1986. Some accounts mention a mountain meridian or independence from India as the reason, but none of the sources found confirmed either.
Fractional offsets that came and went#
These dates come from the IANA database, as of October 2026, and rules can change again.
| Place | What happened |
|---|---|
| North Korea | UTC+8:30 ("Pyongyang Time") from August 15, 2015, to May 5, 2018, then UTC+9 |
| Venezuela | UTC-4:30 from December 9, 2007, to May 1, 2016, then UTC-4 |
| Sri Lanka | UTC+6:30 from May 25, 1996, UTC+6:00 from October 26, 1996, back to UTC+5:30 on April 15, 2006 |
| Iran | UTC+4:30 in summer until 2022. The last clock change was in September 2022, and it has stayed on UTC+3:30 since |
Al Jazeera reported that North Korea's 2015 change marked the 70th anniversary of liberation from Japan. In April 2018, after the inter-Korean summit, the state news agency announced the return to UTC+9 from May 5, as quoted in a post on the IANA time zone mailing list.
How to convert a time with a fractional offset#
The method does not change (How to Convert Time Between Time Zones, Step by Step (With Examples) has the general version). Go through UTC:
- Write each offset in minutes: UTC+5:30 is +330, UTC+5:45 is +345 and UTC-5:00 is -300.
- Subtract the source offset from the target offset to get the gap.
- Add the gap to the time, moving to the next or previous day if you cross midnight.
New York on Thursday, January 15, 2026, is on Eastern Standard Time (UTC-5). India's gap is 330 - (-300) = 630 minutes, or 10 h 30 min, so 9:00 AM in New York is 7:30 PM in India. Nepal's gap is 345 + 300 = 645 minutes, so the same moment is 7:45 PM in Kathmandu. On July 15 New York is on UTC-4, and 9:00 AM becomes 6:30 PM in India and 6:45 PM in Nepal. EST to IST: Time Difference, Conversion Chart and Call Times has a full chart.
That moment, 14:00 UTC on January 15, 2026, in six fractional zones (computed from the IANA data):
| Zone | Local time |
|---|---|
| Tehran (UTC+3:30) | 5:30 PM |
| India (UTC+5:30) | 7:30 PM |
| Nepal (UTC+5:45) | 7:45 PM |
| Eucla (UTC+8:45) | 10:45 PM |
| Adelaide (UTC+10:30) | 12:30 AM on January 16 |
| Chatham Islands (UTC+13:45) | 3:45 AM on January 16 |
Frequently asked questions
Why is India's time zone UTC+5:30?
India uses one standard meridian, 82.5°E, which passes near Allahabad (now Prayagraj). Earth turns 15 degrees an hour, so 82.5 degrees is 5.5 hours of sun time ahead of Greenwich, which gives UTC+5:30. British India adopted it for January 1, 1906, and independent India kept it.
The meridian sits near the middle of a country that spans about 29 degrees of longitude, so it is a compromise. India has no summer time, and its offset does not change in 2026 or 2027.
Which time zones are 45 minutes off?
Three places use a 45-minute offset in 2026: Nepal at UTC+5:45, the Chatham Islands of New Zealand at UTC+12:45 (UTC+13:45 in summer) and the Eucla area of Western Australia at UTC+8:45. Every other fractional zone is on the half hour. This comes from the IANA database, release 2025b, the release bundled with Node 22, as of October 2026.
Why is Nepal's time 15 minutes ahead of India's?
Nepal used India's UTC+5:30 until the start of 1986, then moved its clocks forward 15 minutes to UTC+5:45. Britannica says Nepal picked a time close to the sun time at its capital. Kathmandu's sun time is UTC+5:41:16, so UTC+5:45 is 3 minutes 44 seconds off, while UTC+5:30 would be 11 minutes 16 seconds off. No official reason turned up in searches for this article.
How do I convert a time zone with a 30-minute offset?
Convert to UTC first, then add the offset in minutes. India is +330 minutes, so 14:00 UTC is 19:30 in India. India is 10 hours 30 minutes ahead of New York in winter (UTC-5) and 9 hours 30 minutes ahead in summer (UTC-4).
Will India get a second time zone?
Not as of October 2026, as far as searches could tell. In 2018 the National Physical Laboratory argued that IST-I (UTC+5:30) and IST-II (UTC+6:30, for the northeast and the Andaman and Nicobar Islands) are technically feasible. The government has not adopted that, so IST is the only official time in India.
Sources and further reading
- Half Hour and 45-Minute Time Zones — timeanddate.com
- why are some time zones 30 minutes off instead of an hour — Britannica
- Indian Standard Time — New World Encyclopedia
- When Setting the Clock Divided the Subcontinent — Live History India
- India's timekeeper says country needs two time zones — Down To Earth
- N Korea winds back its clocks to make 'Pyongyang time' — Al Jazeera
- DPRK to revert to UTC+9 from UTC+8:30 — IANA time zone mailing list